I went to the chemical plant for an internship. Not long after I came here, I felt itchy when the weather was hot. I got a red pimple like a scratch when I grabbed it. What happened?

After working in the workshop, there will be a layer of chemicals sticking to your skin, which will happen to me at first. In severe cases, my skin will get red pimples, which is an allergy. Generally, after I finish my work in the workshop, I will take a bath and wash the dirty things off my body. Now I don't have this phenomenon.